publisher: split docs deployment into a workflow

Documentation will now be built using a separated workflow that will be
run whenever publisher finishes. This allows us to use the latest
page deployment code regardless of the commit that triggered publisher.

Some auxilliary changes also come along:

- New deploy-docs workflow can also be run manually.
- "Generated docs" artifacts are now removed. Instead the generated
  documentation will be obtained from the release tarball for Linux.
  This is done since artifacts have a timeout to them, which meddle with
  our ability to run docs deployment at will.
- Implemented basic version segmentation: `/devel` subdirectory will now
  contain the latest devel docs.

.github/workflows/ci.yml

@@ -549,15 +549,6 @@ jobs:
           echo "archive=$archive" >> $GITHUB_OUTPUT
           echo "metadata=$metadata" >> $GITHUB_OUTPUT
 
-      - name: Upload docs to artifacts
-        if: matrix.target.shared_builder
-        uses: actions/upload-artifact@v4
-        with:
-          # If this name is updated, tweak publisher.yml
-          name: Generated docs
-          path: doc/html/
-          if-no-files-found: error
-
       - name: Upload release package to artifacts
         uses: actions/upload-artifact@v4
         with:

.github/workflows/deploy-docs.yml

@@ -0,0 +1,86 @@
+name: Deploy documentation
+on:
+  # Automatically run after any completed publish
+  workflow_run:
+    workflows:
+      - Publish built artifacts
+    types:
+      - completed
+
+  # For manual triggers
+  workflow_dispatch:
+
+# Run every script actions in bash
+defaults:
+  run:
+    shell: bash
+
+concurrency: doc-publisher
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+
+    permissions:
+      id-token: write
+      pages: write
+
+    environment:
+      name: github-pages
+      url: ${{ steps.deploy.outputs.page_url }}
+
+    env:
+      # Triplet to obtain docs from
+      DOC_TARGET: x86_64-linux-gnu
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup latest compiler
+        uses: nim-works/setup-nimskull@0.1.2
+        with:
+          nimskull-version: "*" # Grab the latest nimskull-version
+
+      - name: Compile release_manifest
+        run: nim c -d:release -o:release_manifest tools/release_manifest.nim
+
+      - id: versions
+        name: Grab latest release version
+        run: |
+          # Stolen from asdf-nimskull
+          sort_versions() {
+            sed 'h; s/[+-]/./g; s/$/.z/; G; s/\n/ /' |
+              LC_ALL=C sort -t. -k 1,1n -k 2,2n -k 3,3n -k 4,4 -k 5,5n | awk '{print $2}'
+          }
+
+          all_tags=$(gh release list --json tagName --jq '.[] | .tagName')
+          latest=$(sort_versions <<<"$all_tags" | tail -n 1)
+
+          echo "Latest devel is: $latest"
+          echo "devel=$latest" >> "$GITHUB_OUTPUT"
+        env:
+          GH_TOKEN: ${{ github.token }}
+
+      - name: Construct devel docs
+        run: |
+          tmpdir=$(mktemp -dp "$RUNNER_TEMP" devel.XXXXXXXXXX)
+          # Get the name of the binary archive for the documentation target
+          release_archive=$(gh release download "$DEVEL" -p manifest.json -O - | ./release_manifest -f /dev/stdin get "$DOC_TARGET")
+          # Download the latest release binary
+          gh release download "$DEVEL" -p "$release_archive" -O "$tmpdir/$release_archive"
+          # Extract and remove the top-level directory
+          tar -C "$tmpdir" -xf "$tmpdir/$release_archive" --strip-components=1
+
+          mkdir -p built-docs
+          cp -rT "$tmpdir/doc/html" built-docs/devel
+          cp -rT "$tmpdir/doc/html" built-docs
+        env:
+          GH_TOKEN: ${{ github.token }}
+          DEVEL: ${{ steps.versions.outputs.devel }}
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: built-docs/
+
+      - id: deploy
+        uses: actions/deploy-pages@v4

.github/workflows/publisher.yml

@@ -25,9 +25,6 @@ jobs:
       url: ${{ steps.release.outputs.url }}
 
     steps:
-      # Publish action needs a checkout
-      - uses: actions/checkout@v4
-
       - name: Obtain latest successful run id
         id: finder
         run: |
@@ -48,17 +45,9 @@ jobs:
           WORKFLOW: ci.yml
           CONCLUSION: success
           GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
 
       # Download the latest instance of artifacts from a build done previously
-      - name: Download generated docs
-        uses: actions/download-artifact@v4
-        with:
-          run-id: ${{ steps.finder.outputs.run_id }}
-          # Keep up-to-date with ci.yml
-          name: Generated docs
-          path: doc/html
-          github-token: ${{ github.token }}
-
       - name: Download generated source archive
         uses: actions/download-artifact@v4
         with:
@@ -87,12 +76,6 @@ jobs:
           path: release-staging
           github-token: ${{ github.token }}
 
-      - name: Publish docs
-        uses: JamesIves/github-pages-deploy-action@v4.6.1
-        with:
-          branch: gh-pages
-          folder: doc/html
-
       - id: release-files
         name: Create release manifest
         run: |